The present invention relates to a screwdriver for turning screws, and more specifically to a reversible ratchet screwdriver.
FIGS. 1 and 2 show a reversible ratchet screwdriver according to the prior art. This structure of reversible ratchet screwdriver comprises a handle 10 having a control head 11 at one end, a shank 14 connected to the control head 11, the shank 14 has a ratchet wheel 140 at its rear end and a tubular coupling portion 141 at its front end for holding a tip, a shell 15 mounted around the control head 11, and a locking ring 16 fastened to the control head 11 to lock the shell 15. The control head 11 comprises a storage chamber 111. A forward control pawl 122 and a backward control pawl 123 are mounted in the storage chamber 111, and respectively engaged with the ratchet wheel 140. A ratchet shifter 120 is mounted in an adjustment hole 150 on the shell 15, having shifting strips 121 respectively pressed on the pawls 122;123 for forward/backward shifting control. A locating plate 13 is mounted in a hole on the control head 11 to secure the shank 14 in place. This structure of reversible ratchet screwdriver is still not satisfactory in function. The drawbacks of this structure of reversible ratchet screwdriver is outlined hereinafter.
1. Because the shank 14 is secured to the control head 11 by the locating plate 13, the shank 14 is not replaceable as desired, and the user shall have to prepare a variety of bits for turning different sizes of screws. PA0 2. It is inconvenient to carry a full set of bits with the reversible ratchet screwdriver and to frequently changing the bit from the tubular coupling portion of the shank. PA0 3. It is difficult to install the locating plate and the ratchet shifter in the control head from both sides, and the locating plate and the ratchet shifter tend to slip from position during the assemblage.